public class MyLinkedlist {
    static class ListNode {
        private int val;
        private ListNode prev;
        private ListNode next;

        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;//双向链表的头结点
    public ListNode last;//双向链表的尾结点

        //头插法
        public void addFirst(int data){
                ListNode node = new ListNode(data);
                if(head == null){
                    head = node;
                    last = node;
                }else{
                    node.next = head;
                    head.prev = node;
                    head = node;
                }
        }
        //尾插法
        public void addLast(int data){
            ListNode node = new ListNode(data);
            if(head == null){
                head = node;
                last = node;
            }else{
                node.prev = last;
                last.next = node;
                last = node;
            }
        }
        //任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index,int data){
            ListNode listNode = new ListNode(data);
            if(index < 0 ||index > size()){
                throw new IndexErrorException(index+"下标错误，无法插入");
            }
            if(index == 0){
                addFirst(data);
                return;
            }
            if(index == size()){
                addLast(data);
                return;
            }
            int count = 0;
            ListNode cur = head;
            while(count != index){
                cur = cur.next;
                count++;
            }
            listNode.next = cur;
            listNode.prev = cur.prev;
            cur.prev.next = listNode;
            cur.prev = listNode;
        }
        //查找是否包含关键字key是否在单链表当中
        public boolean contains(int key){
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    return true;
                }
                cur = cur.next;
            }
            return false;
        }
        //删除第一次出现关键字为key的节点
        public void remove(int key){
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    //删除头结点
                    if(cur == head){
                        head = head.next;
                        if(head != null) {
                            head.prev = null;
                        }else{//只有一个节点的情况
                            last = null;
                        }

                    }else {//删除中间和尾巴
                        //删除尾巴
                        if(cur.next == null){
                            cur.prev.next = cur.next;
                            last = last.prev;

                        }else {//删除中间
                            cur.prev.next = cur.next;
                            cur.next.prev = cur.prev;

                        }
                    }
                    return;
                }
                else {
                    cur = cur.next;
                }
            }
        }
        //删除所有值为key的节点
        public void removeAllKey(int key){
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    //删除头结点
                    if(cur == head){
                        head = head.next;
                        if(head != null) {
                            head.prev = null;
                        }else{//只有一个节点的情况
                            last = null;
                        }

                    }else {//删除中间和尾巴
                        //删除尾巴
                        if(cur.next == null){
                            cur.prev.next = cur.next;
                            last = last.prev;

                        }else {//删除中间
                            cur.prev.next = cur.next;
                            cur.next.prev = cur.prev;

                        }
                    }
                }
                cur = cur.next;
            }
        }
        //得到双链表的长度
        public int size(){
            int length = 0;
            ListNode cur = head;
            while(cur != null){
                length++;
                cur = cur.next;
            }
            return length;
        }
        public void display(){
            ListNode cur = head;
            while(cur != null){
                System.out.print(cur.val + " ");
                cur = cur.next;
            }
            System.out.println();
        }
        public void clear(){
            ListNode cur = head;
            while(cur != null){
                ListNode curNext = cur.next;
                cur.prev = null;
                cur.next = null;
                cur = curNext;
            }
            head = null;
            last = null;
            /*
            ListNode cur = head;
            while(cur != null){
            cur.val = null
            cur.prev = null;
            cur = cur.next;
            }
             */
        }

}
